Soybean (Glycine max L. Merr) is a major cash crop and investment commodity in North America and elsewhere. Soybean oil is one of the most widely used edible oils, and soybeans are used worldwide both in animal feed and in human food production. Bacterial pustule, caused by Xanthomonas axonopodis pv. glycines (Xag), is a serious bacterial disease of soybean. Bacterial pustule is widespread in many soybean-growing regions of the world where high temperature and humidity prevail. It is a foliar disease of soybean, with symptoms typically occurring on leaves that include small, pale green spots with elevates pustules, which may develop into large necrotic lesion causing premature defoliation. Bacterial pustule resistance is controlled by a single recessive gene rxp (resistance to Xanthomonas axonopodis). However, two QTL regions were reported in the literature, one was mapped at 3.9 cM from Satt372 and 12.4 cM from Satt014 on linkage group D2 and another mapped at 129.3 cM (Satt108) at LG O. The present invention relates to a newly identified QTL region associated to bacterial pustule resistance at LG C2.
Different varieties of soybean vary in their sensitivity or tolerance to bacterial pustule. Therefore, one of the most effective control measures is planting bacterial pustule tolerant soybean varieties, and thus varietal selection is important for the management of bacterial pustule. However, currently, determining whether a soybean cultivar might have tolerance to bacterial pustule typically involves testing each cultivar in the field or greenhouse under conditions that typically produce bacterial pustule. Thus, the present invention overcomes the shortcomings in the art by providing markers associated with tolerance to bacterial pustule using a novel loci, thereby allowing the characterization of soybean cultivars for bacterial pustule by molecular analysis rather than phenotypic analysis.
Until now bacterial pustule resistance has only been assessed through phenotyping, which can be time consuming and can only be done at late stages of breeding programs, due to its low throughput. This invention describes the discovery of a new QTL region in the soybean genome that is associated with resistance to this pathogen. The ultimate benefit of this invention is to select resistant progenies based on SNP markers at early breeding stages and support the breeding pipeline by filling it in with lines enriched for the resistance allele.
Further, the invention provides a novel loci and/or chromosome interval corresponding to Glycine max chromosome 6 making it possible to select and/or produce commercial soybean plants having increased resistance to bacterial pustule.
SNP markers associated with bacterial pustule resistance in soybean will support selections by the soybean breeding programs on earlier breeding stages and will assure that only plants with desirable (resistance) alleles will be advanced to late stage testing. Also, there is an expected improvement of cost efficiency by eliminating the need of expensive low throughput phenotyping at early breeding stages, thus increasing accuracy of the selection and maximizing the value of investments in field testing. From a trait introgression perspective, the SNP marker can be deployed for rapid introgression of both GM and native traits; expansion of allele frequency for native traits in a broad germplasm base.